It was the first month of my job as a newly qualified teacher. "I'd like you to coach girls' football. You'd be a good role model," the head of year said. "Why a good role model?" I asked. "Because you're straight – you're not one of those fucking dykes."

I was speechless. This teacher knew nothing about me or my opinions, yet he still felt confident enough to make a series of assumptions: first, about my sexuality; second, that I would not be offended by his words; and third, that it was an appropriate statement to make in a staff room, surrounded by fellow teachers. This third presumption in particular implied a collective failing towards every child and adolescent at the school.

I did not have much experience, but I knew this was not right. I confided in various colleagues and tried to make a complaint. At every turn I was met with a similar response: "Oh I'm sure he was just joking/he's just being a typical guy/don't take it so seriously". Not one person I spoke to recognised the severity of what I had heard. The fact that my colleagues and the institution itself appeared to collude, albeit passively, in this homophobia, made this all the worse.

The real tragedy in this, of course, was not the offence that I felt; it was the fact that this teacher had significant influence over hundreds of teenagers.

A good number of these young people may have been straight, some may have been beginning to question their sexuality, others may have been gay or have had family members and friends who were; but regardless of this, every single one of them needed to learn in an environment where bigotry and intolerance were not welcome.

A YouGov poll, commissioned by Stonewall, discovered that 43% of secondary school teachers have heard homophobic comments from their colleagues. Today no teacher who made racist remarks would escape widespread rebuke; so why is homophobia still tolerated?

A teacher is required to educate, enlighten and inspire yet also to give pastoral support, to help a child navigate through possibly the most challenging and daunting time of his or her life. How can a homophobic teacher deal with the myriad problems young people face, especially incidences of homophobic bullying among the pupils?

For a child, the school setting needs to be a place where all forms of bullying are challenged and steadfastly rejected. Teachers are the key agents in ensuring that this is the case and young people must be sure of equality and acceptance in the eyes of their educators.

The same YouGov poll heard that 90% of teachers have never received any training on homophobic bullying. If schools are not prepared to tackle homophobia and foster a culture where pupils and teachers can confidently report such discrimination, then the government needs to step into the breach. If educators are serious about building a more tolerant, enlightened society, then no form of discrimination from those who have such great influence over young people can go unchallenged.

Since that initial conversation with my overtly homophobic colleague, I have encountered a whole variety of outlooks and opinions that would register on the homophobia spectrum. It still shocks me every time an otherwise friendly member of staff makes a comment about "pansies", or a respected colleague tells me of his aversion to watching Sean Penn's Oscar-winning performance in Milk because he "can't stand that kind of thing".

Pupils may well be forging ahead in tolerance where teachers are failing to lead. It is my experience that it is often young people who are the most accepting members of a school community, and as a consequence they put many of their teachers to shame. Before the government can credibly begin to talk about tackling homophobic bullying among pupils, it should ensure that educators are not perpetrating this discrimination themselves.